1 2 Previous Next 15 Replies Latest reply: Jan 8, 2014 1:02 PM by Jan Hedlund
SG1776 Level 1 Level 1 (0 points)

For a Mac Plus keyboard cable, can I substitute a phone cable or is the Mac jack wiring specialized?

  • 1. Re: Mac Plus keyboard cable
    Jan Hedlund Level 6 Level 6 (8,955 points)

    No, it is not the same. In order to avoid damage to any circuits, I recommend an Internet search for details about the correct wiring/pinouts. See also:

     

    http://support.apple.com/kb/TA29935

     

    Jan

  • 2. Re: Mac Plus keyboard cable
    Appaloosa mac man Level 5 Level 5 (4,325 points)

    Jan,

     

    I took a look at the support article kb/TA29935.  As I read it, it does not indicate the pin position for both ends which means that the article, in and of itself, does not rule out the use of standard flat phone wiire. 

     

    I dug a keyboard and cable out of storage.  If SG1776 is still following this post, I will test the cable.  The cable is flat phone cable and not twisted pair.  A simple concontinuity tester should let me confirm the wire positions.  If positions 1-2-3-4 on one end connect to positions 1-2-3-4 on the other end, and a four pin phone wire does the same, without trading positions, then he should be OK.  The second option would be for him to build his own phone cable with a crimping tool.

     

    Ji~m

  • 3. Re: Mac Plus keyboard cable
    Jan Hedlund Level 6 Level 6 (8,955 points)

    Hi Jim,

     

    According to a section 9.1.3 of the Classic Mac Repair Notes by Thomas H. Lee, the connections are reversed on one end. That means that it should be possible to modify a cable, but you would have to know exactly how to do it in order to avoid damages.

     

    Jan

  • 4. Re: Mac Plus keyboard cable
    SG1776 Level 1 Level 1 (0 points)

    Is everyone agreed that phone cable needs modification? Also, where can I get a Mac cable?

  • 5. Re: Mac Plus keyboard cable
    Appaloosa mac man Level 5 Level 5 (4,325 points)

    In Washington state, Seattle is the best location for recyclers who care about saving older Mac components.  RE-PC sets aside older Mac and Apple items for public resale.  We closed down the last "used mac only" store in Spokane - eastern WA in 1999.  We have leftovers that we use for youth educational projects.  We can test, we are not set up for mail order sales.  What is the largest city near you?  Maybe we know a contact.''

     

    Ji~m

  • 6. Re: Mac Plus keyboard cable
    SG1776 Level 1 Level 1 (0 points)

    Bahstan, MA.

  • 7. Re: Mac Plus keyboard cable
    Appaloosa mac man Level 5 Level 5 (4,325 points)

    I recall a PBS episode of 'This Old House' that took place in your neck of the woods.  There was a big push for recycling and salvage.  I can not imagine not having some shop in town that has set aside older gear for the die hards.  Push come to shove, we could mail a cable off to you.  Making your own cable would be easier.  We will verify the pin outs and post back.

     

    http://www.bmac.org/contacts.html shows a list of individuals who should know who would know or have resources. 

    _"W. 'Ian' Blanton has been involved with the Macintosh from the time in 1988, when he kicked out the power-plug from his roommates brand new Mac II series and thought he killed it, to being network admin for an entire Air Force base full of macs. He currently works for Tech Superpowers as the Director of Onsite Consulting, where he continues to hone his razor-like Mac skills. If you're into torment, you can read his Weblog._Email Ian 

     

    Also, Grant is from Boston and might know some resources.

  • 8. Re: Mac Plus keyboard cable
    Jan Hedlund Level 6 Level 6 (8,955 points)

    Hi,

     

    >Is everyone agreed that phone cable needs modification?

     

    If I place the two plugs of a Macintosh Plus keyboard cable next to each other (side by side) on a table, both pointing in the same direction, with both tabs up, the wires are arranged as follows:

    yellow-green-red-black  yellow-green-red-black

     

    Placing the two plugs of a handset cable from one Swedish telephone the same way, results in the following:

    yellow-green-red-black  black-red-green-yellow

     

    Both cables use the same type of plug (4P4C).

     

    As shown by this simple comparison, at least these two cables are different.

     

    See also the 'Data port' text in this article:

    http://en.wikipedia.org/wiki/4P4C#4P4C

     

    In the case of the Swedish telephone handset cable above, it appears as if turning one of the two plugs 180 degrees (using a crimping tool) would result in a cable that could be used for a keyboard. However, this is not a recommendation. Proceed at your own  risk if you decide to carry on with any experimental modifications. I have not tested any modified cables.

     

    You should check whether randomly chosen telephone handset cables in your country have the same wiring/colours as the one I examined.

     

    Jim may also want to verify the wiring and colours with another Macintosh Plus keyboard cable.

     

    Jan

  • 9. Re: Mac Plus keyboard cable
    Appaloosa mac man Level 5 Level 5 (4,325 points)

    Jan,

     

    You are absolutely right.  The pin position and color are as you said with one clairification.  Yellow-green-red-black is reading right to left with the metal contacts facing up.  What matters most is that the wire in position one - reading right to left or left to right - is identical for both ends.  Phones wires are reversed.

     

    As for the quality of phone cable used, the flat lead wire is fairly universal.  I would not be afraid to build my own cable. 

     

    Once twisted pair was introduced for high speed transmission, ie. cat 5 cable, wire grades became more important.

     

    A quick review of phone history might be in order.  Rotary Pulse dialed phones worked with pairs of wires.  Red/Green were the inner pair and Black and yellow were the outer pair.  Any pair of wires would work.  With the advent of touch tone phones, polarity mattered.  With the wrong polarity of wires, dialing a touch tone resulted in a 'thud' sound and not distinctive tones.  What did not matter is whether you used the inner pair or outer pair.

     

    Ji`~m

     

    Happy New Year.  You celebrated long before we did!

  • 10. Re: Mac Plus keyboard cable
    Jan Hedlund Level 6 Level 6 (8,955 points)

    Jim,

     

    Happy New Year to you, too!

     

    Via reference 6. in the Wikipedia article above, I found the following web page, which also verifies the keyboard cable wiring and colours:

    http://blog.syrinxsystems.co.uk/mac-plus-keyboard-cable/#more-172

     

    As an experiment, I am going to buy some 4P4C plugs and then using a crimping tool

    a) modify a coiled telephone handset cord (cutting off one of the plugs, replacing it with a new one turned 180 degrees)

    and/or

    b) build a completely new keyboard cable (standard 4-lead cable, two new plugs).

    The cable(s) can then be tested with a Macintosh Plus. Providing (of course) that the correct wiring is used, it should be OK.

     

    Jan

  • 11. Re: Mac Plus keyboard cable
    Jan Hedlund Level 6 Level 6 (8,955 points)

    A new keyboard cable was built using a low-cost crimping tool. After a test with a Macintosh Plus, I can now confirm that everything works well.

     

    A standard (flat) 4-lead phone cable and two 4P4C modular plugs were used. The plastic tool in question had a small adapter piece, needed to correctly position the narrow 4P4C plug.

     

    As indicated earlier, for this keyboard cable, the wires/colours are identical in both plugs. For example, if one holds the two plugs side by side (upright, with the cable openings down) while looking at the locking tabs, the wire colours are:

     

    yellow  green  red  black        yellow  green  red  black

     

    Jan

  • 12. Re: Mac Plus keyboard cable
    SG1776 Level 1 Level 1 (0 points)

    This seems a possibility but Ive read, maybe here, that modified phone cables may be weak or possibly dangerous to the Mac in some way. And even if modification is good, a crimping tool may cost as much as a keyboard cable.

  • 13. Re: Mac Plus keyboard cable
    Jan Hedlund Level 6 Level 6 (8,955 points)

    Hi,

     

    A "real" keyboard cable for a Macintosh Plus appears to be made from a (coiled) phone-style flat cable and standard-looking 4P4C plugs, so I do not think that a modified cable as such would differ in any significant way.

     

    However, it is extremely important to connect the wires correctly when building a custom cable. Otherwise, there is a substantial risk of reversed polarity, which could destroy the computer and/or the keyboard. For more information, see the document (web search) mentioned in my second message and the page (link) mentioned in my fourth message. Do not use a normal ready-made telephone/handset cable (with plugs) in connection with a Macintosh Plus.

     

    Also, pay special attention to the crimping quality in order to avoid unreliable connections and short-circuits.

     

    You can probably find a simple crimping tool (that can handle 4P4C, in addition to the broader modular plugs) for around USD 20.

     

    Jan

  • 14. Re: Mac Plus keyboard cable
    SG1776 Level 1 Level 1 (0 points)

    On a site for old Macs, somebody said that even a properly modified phone cable would or may have small? problems but I dont recall the specifics except, I believe, that a longer cable may have a weak or distorted signal.

     

    Does an original keyboard cable cost more than $20?! I got my Mac+ at a yard sale for free. So one must also buy plugs? Is there a problems removing the old plug and attaching the new?

1 2 Previous Next